This invention relates generally to shields and shade apparatus for reducing the solar heat gain of building structures, and in particular to a roof-mounted fabric shade panel that is periodically misted with water to improve the transfer of thermal energy from a building structure to the surrounding atmosphere by wind convection and (evaporative cooling.
Heat, a form of kinetic energy, is transferred in three ways: conduction, convection and radiation. The transfer of heat energy by radiation makes possible the transfer of large amounts of heat from the sun to the earth. During the summer months, the roof of a building structure becomes quite hot because of radiation from the sun. Conduction carries the heat through the roof where it is distributed into the attic space by radiation and convection. The flow of heat through the roof can be reduced somewhat by applying insulation to the underside of the roof. Also, heated air in the attic space may be removed through vent louvers in the roof.
Comfort air conditioning refers to control of living spaces inhabited by people to promote their comfort, health or productivity. Spaces in which air is conditioned for comfort include houses, office buildings, hotels and factory work areas. Heat is transmitted through all parts of the building structure, which includes walls, floors, ceilings and windows. Whether heat enters or leaves the building space depends upon whether the outside building surfaces are warmer or cooler than the inside surfaces. Thermal insulation is installed, typically in the attic and walls, to reduce the overall thermal conductance of the building enclosure.
Solar heating represents a large percentage of heat gain through walls and roofs of building structures. During daylight hours, a building structure acts as a heat sink, and absorbs large quantities of thermal energy from the sun. This thermal energy is conducted and radiated throughout the building, with the result that the temperature of the living space within the building will rise. Comfort air conditioning is employed to maintain the temperature and humidity of air within the living space within acceptable limits.
Some commercial building structures have a flat, tar-and-gravel-type roof with air conditioning units mounted on the roof. During daylight hours, especially on non-cloudy days, radiant solar energy causes heating of the roof material and of the air conditioning units. In turn, heat is conducted through the roof into the ceiling and walls of the building structure. The radiant solar heat increases the overall skin temperature or surface temperature of the building structure, and results in an increase in the ambient air temperature within the living space enclosed by the structure. This increases the work load on the air conditioning system and results in a corresponding increase in the energy operating costs for that structure.
The practice of artificial shading has been applied extensively for various purposes, including the shading of outdoor activity spaces, for example patios, play areas, walkways and the like. Various coverings and shields have been proposed for building shade and cooling purposes. The following U.S. patents are representative of the prior art in the field of this invention:
______________________________________ U.S. Pat. No. Inventor Title of Invention ______________________________________ 5,598,719 Jones et al Evaporative Cooling Appa- ratus 5,497,633 Jones et al Evaporative Cooling Unit 4,498,262 Garcia Solar Shield Assembly 5,502,929 Daniels Combination Wind and Sun Barrier 4,730,423 Hughes Apparatus and Method for Protecting Cooling Units 4,732,012 Thorpe Energy Efficient Evapora- tive Cooler Cover Appara- tus 3,788,542 Mee Environmental Control Method and Apparatus ______________________________________
U.S. Pat. Nos. 5,598,719 and 5,497,633 disclose an overhead pavilion structure on which spray nozzles are mounted for producing a mist or fog within a lounge area underlying the structure, with the air temperature being reduced by evaporative cooling. The overhead structure is provided by upright conduits through which pressurized air is circulated.
U.S. Pat. No. 4,498,262 discloses a solar shield assembly in which metal panels are suspended above a building roof structure for blocking solar radiation.
U.S. Pat. No. 5,502,929 discloses perforated steel barrier panels mounted on upright posts for blocking wind flow and for providing shade.
U.S. Pat. No. 4,730,423 discloses a vinyl-coated fiberglass screen that is mounted on support posts for shielding an air conditioning unit from direct solar radiation.
U.S. Pat. No. 4,732,012 discloses an energy-saving panel composed of thermal insulation material for protecting an air conditioning unit from direct solar radiation.
U.S. Pat. No. 3,788,542 discloses a water spray nozzle for producing fog/mist within a greenhouse enclosure.